Labels are attached to containers for advertisement and appearance. In large commercial applications, labels are applied to substrate containers or goods with high speed equipment. High speed equipment transfers the label, or facestock, from a liner release sheet to the substrate container. Heretofore, the facestock has been at least 3.4 mils thick. The backing or liner material has been paper or a polymeric film such as polyethylene terephthalate. Thicknesses of the liner have varied, but paper liners have been at least 2.2 mils thick and more often at least 2.5 mils thick.
Ultra thin facestock having thickness a low as 0.7 mils is known when biaxially oriented polypropylene has been used for label facestock material in combination with polyethylene terephthalate (PET) liner material. Biaxially oriented polypropylene is stiff and even very thin biaxially oriented polypropylene having a thickness as low as 0.5 mils can lend itself to high speed label mounting operations. In these operations the label facestock for very small periods of time hangs in air after the liner, such as a polyethylene terephthalate liner, has been removed from the facestock during application of the label. The PET is tough and smooth, and hence, can be relatively thin. PET is smooth and will protect the clarity of polypropylene film. Paper liners are cheaper, but are too rough and put the clarity of polypropylene at risk. The toughness of PET will protect the thin low tensile strength of the polypropylene facestock label.
Polypropylene film facestock, however, is not without problems. Without a top coating, printing on the film surface scratches and needs to be over-coated with lacquer or layered with another polypropylene to mitigate scratching. Moreover, polypropylene is not readily printable as other films such as polyethylene. While polyethylene needs to be surface treated, such as with a corona treatment, to enhance printability, it is still less costly to corona treat polyethylene for printability than to over-coat polypropylene to mitigate scratching and enhance printability. Moreover, the stiffness of polypropylene works against its use on flexible substrates, such as squeezable bottles, where deformation of the label is important.
United States Patent Publication 2003/0152722 of Fearn et al. describes thin film facestock labels of 1 mil or less in conjunction with a polyester film release liner. This publication refers to the facestock films as polypropylene, polyethylene or PVC, but describes biaxially oriented polypropylene as “exemplary”. Even if this polyethylene film is used for facestock, the publication appears to suggest that it should be biaxially oriented (as is the case with polypropylene), to attain sufficient stiffness for the film.
United States Patent Publication 2001/0030030 of Nandy et al. describes film label stock of polypropylene and polyethylene having a thickness of 2 mils laminated with a polyester release liner.
As with polypropylene films, the use of polyester liners, such as polyethylene terephthalate, has been thought necessary when attempting to produce extremely thin labels with thin polyethylene films. As can be seen from the Fearn et al. publication, the use of ink as well as biaxially oriented film has been thought necessary for the thin films to have sufficient strength and stiffness to survive high speed production conditions and avoid tearing and stretching. The polyester liners cause as well as solve problems. While they may strengthen the label stock, they also cause static electricity in the label stock which creates materials handling problems. Moreover, ultra thin facestocks also have required over lamination with another film to achieve sufficient durability for labeling operations.
U.S. Pat. No. 5,380,572 to Kotani et al. describes transparent pressure sensitive polyethylene labels. It does not specify the thickness of the polyethylene facestock used, but rather in a description of prior art generally describes a “label sheet” having 25 to 250 μm. This statement was made, however, in conjunction with the general utilization of rather stiff films such as PET and polyvinyl chloride films. Kotani et al. note that these stiff films can not be matched with flexible container substrates. In short, Kotani et al. does not suggest the use of thin polyethylene films for labels, especially in conjunction with inexpensive thin paper liners.
U.S. Pat. No. 4,587,158 to Ewing and its reissue patent, Re. 32,929, describe deformable polyethylene labels for squeezable bottles and other deformable substrates. Kotani et al. describe Ewing's labels at low densities as being fragile, especially very thin films with low densities. Ewing's films have thicknesses in the range of 0.05 mm to 0.127 mm at densities of from 0.910 to 0.925 g/cm3 and from 0.076 mm to 0.0127 mm at densities of from 0.925 to 0.940 g/cm3. At higher densities and thicknesses, Ewing's labels will inherently not have the clarity of the very thin film labels having relatively low densities.
U.S. Pat. No. 6,099,927 to Freedman describes die cut film labels having a thickness of less than 3 mils, e.g. 2 to 3 mils, but does not suggest the ultra thin facestock or the thin facestock with a thin liner as described in connection with the instant invention.